Ion Exchange - A company in Harper's Ferry, NE Iowa - (800) 291-2143
native wildflowers and seeds - has milkweed plugs/plants you can order
Prairie Moon Nursery - rural Winona County in southeast Minnesota
Monarch Favorites - Nectar Sources and Larval Host Plants
Monarch Watch Milkweed Market
Monarch Watch: Monarch Waystation Seed kits
Xerces.org - Milkweed seed finder - Search for where to get seeds
Swift Greenhouses, Inc - Supplier for Iowa, listed under Monarch Watch as pesticide free - Look for their name/logo on the back of description labels on plants in garden centers.